3 perlintern - autogenerated documentation of purely B<internal>
7 X<internal Perl functions> X<interpreter functions>
9 This file is the autogenerated documentation of functions in the
10 Perl interpreter that are documented using Perl's internal documentation
11 format but are not marked as part of the Perl API. In other words,
12 B<they are not for use in extensions>!
15 =head1 CV reference counts and CvOUTSIDE
22 Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
23 CV (if any). Because pointers to anonymous sub prototypes are
24 stored in C<&> pad slots, it is a possible to get a circular reference,
25 with the parent pointing to the child and vice-versa. To avoid the
26 ensuing memory leak, we do not increment the reference count of the CV
27 pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
28 has a C<&> pad slot pointing back to us. In this case, we set the
29 C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
30 circumstances we should decrement the refcount of the parent when freeing
33 There is a further complication with non-closure anonymous subs (i.e. those
34 that do not refer to any lexicals outside that sub). In this case, the
35 anonymous prototype is shared rather than being cloned. This has the
36 consequence that the parent may be freed while there are still active
39 BEGIN { $a = sub { eval '$x' } }
41 In this case, the BEGIN is freed immediately after execution since there
42 are no active references to it: the anon sub prototype has
43 C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
44 CV, so it doesn't contribute to BEGIN's refcount either. When $a is
45 executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
46 and the freed BEGIN is accessed.
48 To avoid this, whenever a CV and its associated pad is freed, any
49 C<&> entries in the pad are explicitly removed from the pad, and if the
50 refcount of the pointed-to anon sub is still positive, then that
51 child's C<CvOUTSIDE> is set to point to its grandparent. This will only
52 occur in the single specific case of a non-closure anon prototype
53 having one or more active references (such as C<$a> above).
55 One other thing to consider is that a CV may be merely undefined
56 rather than freed, eg C<undef &foo>. In this case, its refcount may
57 not have reached zero, but we still delete its pad and its C<CvROOT> etc.
58 Since various children may still have their C<CvOUTSIDE> pointing at this
59 undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
60 the chain of lexical scopes is unbroken. For example, the following
64 sub tmp { sub { eval '$x' } }
69 bool CvWEAKOUTSIDE(CV *cv)
77 =head1 Functions in file pad.h
85 Save the current pad in the given context block structure.
87 void CX_CURPAD_SAVE(struct context)
95 Access the SV at offset po in the saved current pad in the given
96 context block structure (can be used as an lvalue).
98 SV * CX_CURPAD_SV(struct context, PADOFFSET po)
106 Get the value from slot C<po> in the base (DEPTH=1) pad of a padlist
108 SV * PAD_BASE_SV(PADLIST padlist, PADOFFSET po)
117 Clone the state variables associated with running and compiling pads.
119 void PAD_CLONE_VARS(PerlInterpreter *proto_perl \)
124 =item PAD_COMPNAME_FLAGS
125 X<PAD_COMPNAME_FLAGS>
127 Return the flags for the current compiling pad name
128 at offset C<po>. Assumes a valid slot entry.
130 U32 PAD_COMPNAME_FLAGS(PADOFFSET po)
135 =item PAD_COMPNAME_GEN
138 The generation number of the name at offset C<po> in the current
139 compiling pad (lvalue). Note that C<SvCUR> is hijacked for this purpose.
141 STRLEN PAD_COMPNAME_GEN(PADOFFSET po)
146 =item PAD_COMPNAME_GEN_set
147 X<PAD_COMPNAME_GEN_set>
149 Sets the generation number of the name at offset C<po> in the current
150 ling pad (lvalue) to C<gen>. Note that C<SvCUR_set> is hijacked for this purpose.
152 STRLEN PAD_COMPNAME_GEN_set(PADOFFSET po, int gen)
157 =item PAD_COMPNAME_OURSTASH
158 X<PAD_COMPNAME_OURSTASH>
160 Return the stash associated with an C<our> variable.
161 Assumes the slot entry is a valid C<our> lexical.
163 HV * PAD_COMPNAME_OURSTASH(PADOFFSET po)
168 =item PAD_COMPNAME_PV
171 Return the name of the current compiling pad name
172 at offset C<po>. Assumes a valid slot entry.
174 char * PAD_COMPNAME_PV(PADOFFSET po)
179 =item PAD_COMPNAME_TYPE
182 Return the type (stash) of the current compiling pad name at offset
183 C<po>. Must be a valid name. Returns null if not typed.
185 HV * PAD_COMPNAME_TYPE(PADOFFSET po)
195 void PAD_DUP(PADLIST dstpad, PADLIST srcpad, CLONE_PARAMS* param)
200 =item PAD_RESTORE_LOCAL
203 Restore the old pad saved into the local variable opad by PAD_SAVE_LOCAL()
205 void PAD_RESTORE_LOCAL(PAD *opad)
213 Save the current pad to the local variable opad, then make the
214 current pad equal to npad
216 void PAD_SAVE_LOCAL(PAD *opad, PAD *npad)
221 =item PAD_SAVE_SETNULLPAD
222 X<PAD_SAVE_SETNULLPAD>
224 Save the current pad then set it to null.
226 void PAD_SAVE_SETNULLPAD()
234 Set the slot at offset C<po> in the current pad to C<sv>
236 SV * PAD_SETSV(PADOFFSET po, SV* sv)
244 Set the current pad to be pad C<n> in the padlist, saving
245 the previous current pad. NB currently this macro expands to a string too
246 long for some compilers, so it's best to replace it with
249 PAD_SET_CUR_NOSAVE(padlist,n);
252 void PAD_SET_CUR(PADLIST padlist, I32 n)
257 =item PAD_SET_CUR_NOSAVE
258 X<PAD_SET_CUR_NOSAVE>
260 like PAD_SET_CUR, but without the save
262 void PAD_SET_CUR_NOSAVE(PADLIST padlist, I32 n)
270 Get the value at offset C<po> in the current pad
272 void PAD_SV(PADOFFSET po)
280 Lightweight and lvalue version of C<PAD_SV>.
281 Get or set the value at offset C<po> in the current pad.
282 Unlike C<PAD_SV>, does not print diagnostics with -DX.
283 For internal use only.
285 SV * PAD_SVl(PADOFFSET po)
293 Clear the pointed to pad value on scope exit. (i.e. the runtime action of 'my')
295 void SAVECLEARSV(SV **svp)
303 save PL_comppad and PL_curpad
317 Save a pad slot (used to restore after an iteration)
319 XXX DAPM it would make more sense to make the arg a PADOFFSET
320 void SAVEPADSV(PADOFFSET po)
328 =head1 Functions in file pp_ctl.c
336 Locate the CV corresponding to the currently executing sub or eval.
337 If db_seqp is non_null, skip CVs that are in the DB package and populate
338 *db_seqp with the cop sequence number at the point that the DB:: code was
339 entered. (allows debuggers to eval in the scope of the breakpoint rather
340 than in the scope of the debugger itself).
342 CV* find_runcv(U32 *db_seqp)
345 Found in file pp_ctl.c
350 =head1 Global Variables
357 When Perl is run in debugging mode, with the B<-d> switch, this SV is a
358 boolean which indicates whether subs are being single-stepped.
359 Single-stepping is automatically turned on after every step. This is the C
360 variable which corresponds to Perl's $DB::single variable. See
366 Found in file intrpvar.h
371 When Perl is run in debugging mode, with the B<-d> switch, this GV contains
372 the SV which holds the name of the sub being debugged. This is the C
373 variable which corresponds to Perl's $DB::sub variable. See
379 Found in file intrpvar.h
384 Trace variable used when Perl is run in debugging mode, with the B<-d>
385 switch. This is the C variable which corresponds to Perl's $DB::trace
386 variable. See C<PL_DBsingle>.
391 Found in file intrpvar.h
396 The C variable which corresponds to Perl's $^W warning variable.
401 Found in file intrpvar.h
406 The GV which was last used for a filehandle input operation. (C<< <FH> >>)
411 Found in file thrdvar.h
416 The output field separator - C<$,> in Perl space.
421 Found in file thrdvar.h
426 The input record separator - C<$/> in Perl space.
431 Found in file thrdvar.h
443 Returns C<TRUE> if given the name of a magical GV.
445 Currently only useful internally when determining if a GV should be
446 created even in rvalue contexts.
448 C<flags> is not used at present but available for future extension to
449 allow selecting particular classes of magical variable.
451 Currently assumes that C<name> is NUL terminated (as well as len being valid).
452 This assumption is met by all callers within the perl core, which all pass
453 pointers returned by SvPV.
455 bool is_gv_magical(const char *name, STRLEN len, U32 flags)
460 =item is_gv_magical_sv
463 Returns C<TRUE> if given the name of a magical GV. Calls is_gv_magical.
465 bool is_gv_magical_sv(SV *name, U32 flags)
473 =head1 Hash Manipulation Functions
477 =item refcounted_he_chain_2hv
478 X<refcounted_he_chain_2hv>
480 Generates an returns a C<HV *> by walking up the tree starting at the passed
481 in C<struct refcounted_he *>.
483 HV * refcounted_he_chain_2hv(const struct refcounted_he *c)
488 =item refcounted_he_free
489 X<refcounted_he_free>
491 Decrements the reference count of the passed in C<struct refcounted_he *>
492 by one. If the reference count reaches zero the structure's memory is freed,
493 and C<refcounted_he_free> iterates onto the parent node.
495 void refcounted_he_free(struct refcounted_he *he)
500 =item refcounted_he_new
503 Creates a new C<struct refcounted_he>. As S<key> is copied, and value is
504 stored in a compact form, all references remain the property of the caller.
505 The C<struct refcounted_he> is returned with a reference count of 1.
507 struct refcounted_he * refcounted_he_new(struct refcounted_he *const parent, SV *const key, SV *const value)
522 Function called by C<do_readline> to spawn a glob (or do the glob inside
523 perl on VMS). This code used to be inline, but now perl uses C<File::Glob>
524 this glob starter is only used by miniperl during the build process.
525 Moving it away shrinks pp_hot.c; shrinking pp_hot.c helps speed perl up.
527 PerlIO* start_glob(SV* pattern, IO *io)
535 =head1 Magical Functions
542 Triggered by a delete from %^H, records the key to C<PL_compiling.cop_hints>.
544 int magic_sethint(SV* sv, MAGIC* mg)
552 Copy some of the magic from an existing SV to new localized version of
553 that SV. Container magic (eg %ENV, $1, tie) gets copied, value magic
554 doesn't (eg taint, pos).
556 void mg_localize(SV* sv, SV* nsv)
564 =head1 Pad Data Structures
571 CV's can have CvPADLIST(cv) set to point to an AV.
573 For these purposes "forms" are a kind-of CV, eval""s are too (except they're
574 not callable at will and are always thrown away after the eval"" is done
575 executing). Require'd files are simply evals without any outer lexical
578 XSUBs don't have CvPADLIST set - dXSTARG fetches values from PL_curpad,
579 but that is really the callers pad (a slot of which is allocated by
582 The CvPADLIST AV has does not have AvREAL set, so REFCNT of component items
583 is managed "manual" (mostly in pad.c) rather than normal av.c rules.
584 The items in the AV are not SVs as for a normal AV, but other AVs:
586 0'th Entry of the CvPADLIST is an AV which represents the "names" or rather
587 the "static type information" for lexicals.
589 The CvDEPTH'th entry of CvPADLIST AV is an AV which is the stack frame at that
590 depth of recursion into the CV.
591 The 0'th slot of a frame AV is an AV which is @_.
592 other entries are storage for variables and op targets.
595 C<PL_comppad_name> is set to the names AV.
596 C<PL_comppad> is set to the frame AV for the frame CvDEPTH == 1.
597 C<PL_curpad> is set to the body of the frame AV (i.e. AvARRAY(PL_comppad)).
599 During execution, C<PL_comppad> and C<PL_curpad> refer to the live
600 frame of the currently executing sub.
602 Iterating over the names AV iterates over all possible pad
603 items. Pad slots that are SVs_PADTMP (targets/GVs/constants) end up having
604 &PL_sv_undef "names" (see pad_alloc()).
606 Only my/our variable (SVs_PADMY/SVs_PADOUR) slots get valid names.
607 The rest are op targets/GVs/constants which are statically allocated
608 or resolved at compile time. These don't have names by which they
609 can be looked up from Perl code at run time through eval"" like
610 my/our variables can be. Since they can't be looked up by "name"
611 but only by their index allocated at compile time (which is usually
612 in PL_op->op_targ), wasting a name SV for them doesn't make sense.
614 The SVs in the names AV have their PV being the name of the variable.
615 NV+1..IV inclusive is a range of cop_seq numbers for which the name is
616 valid. For typed lexicals name SV is SVt_PVMG and SvSTASH points at the
617 type. For C<our> lexicals, the type is also SVt_PVGV, with the MAGIC slot
618 pointing at the stash of the associated global (so that duplicate C<our>
619 declarations in the same package can be detected). SvCUR is sometimes
620 hijacked to store the generation number during compilation.
622 If SvFAKE is set on the name SV, then that slot in the frame AV is
623 a REFCNT'ed reference to a lexical from "outside". In this case,
624 the name SV does not use NVX and IVX to store a cop_seq range, since it is
625 in scope throughout. Instead IVX stores some flags containing info about
626 the real lexical (is it declared in an anon, and is it capable of being
627 instantiated multiple times?), and for fake ANONs, NVX contains the index
628 within the parent's pad where the lexical's value is stored, to make
631 If the 'name' is '&' the corresponding entry in frame AV
632 is a CV representing a possible closure.
633 (SvFAKE and name of '&' is not a meaningful combination currently but could
634 become so if C<my sub foo {}> is implemented.)
636 Note that formats are treated as anon subs, and are cloned each time
637 write is called (if necessary).
639 The flag SVf_PADSTALE is cleared on lexicals each time the my() is executed,
640 and set on scope exit. This allows the 'Variable $x is not available' warning
641 to be generated in evals, such as
643 { my $x = 1; sub f { eval '$x'} } f();
645 AV * CvPADLIST(CV *cv)
653 Clone a CV: make a new CV which points to the same code etc, but which
654 has a newly-created pad built by copying the prototype pad and capturing
657 CV* cv_clone(CV* proto)
665 dump the contents of a CV
667 void cv_dump(const CV *cv, const char *title)
675 Dump the contents of a padlist
677 void do_dump_pad(I32 level, PerlIO *file, PADLIST *padlist, int full)
685 "Introduce" my variables to visible status.
695 Add an anon code entry to the current compiling pad
697 PADOFFSET pad_add_anon(SV* sv, OPCODE op_type)
705 Create a new name and associated PADMY SV in the current pad; return the
707 If C<typestash> is valid, the name is for a typed lexical; set the
708 name's stash to that value.
709 If C<ourstash> is valid, it's an our lexical, set the name's
710 OURSTASH to that value
712 If fake, it means we're cloning an existing entry
714 PADOFFSET pad_add_name(const char *name, HV* typestash, HV* ourstash, bool clone, bool state)
722 Allocate a new my or tmp pad entry. For a my, simply push a null SV onto
723 the end of PL_comppad, but for a tmp, scan the pad from PL_padix upwards
724 for a slot which has no name and no active value.
726 PADOFFSET pad_alloc(I32 optype, U32 tmptype)
731 =item pad_block_start
734 Update the pad compilation state variables on entry to a new block
736 void pad_block_start(int full)
744 Check for duplicate declarations: report any of:
745 * a my in the current scope with the same name;
746 * an our (anywhere in the pad) with the same name and the same stash
748 C<is_our> indicates that the name to check is an 'our' declaration
750 void pad_check_dup(const char* name, bool is_our, const HV* ourstash)
758 Find a named lexical anywhere in a chain of nested pads. Add fake entries
759 in the inner pads if it's found in an outer one.
761 Returns the offset in the bottom pad of the lex or the fake lex.
762 cv is the CV in which to start the search, and seq is the current cop_seq
763 to match against. If warn is true, print appropriate warnings. The out_*
764 vars return values, and so are pointers to where the returned values
765 should be stored. out_capture, if non-null, requests that the innermost
766 instance of the lexical is captured; out_name_sv is set to the innermost
767 matched namesv or fake namesv; out_flags returns the flags normally
768 associated with the IVX field of a fake namesv.
770 Note that pad_findlex() is recursive; it recurses up the chain of CVs,
771 then comes back down, adding fake entries as it goes. It has to be this way
772 because fake namesvs in anon protoypes have to store in NVX the index into
775 PADOFFSET pad_findlex(const char *name, const CV* cv, U32 seq, int warn, SV** out_capture, SV** out_name_sv, int *out_flags)
783 Given a lexical name, try to find its offset, first in the current pad,
784 or failing that, in the pads of any lexically enclosing subs (including
785 the complications introduced by eval). If the name is found in an outer pad,
786 then a fake entry is added to the current pad.
787 Returns the offset in the current pad, or NOT_IN_PAD on failure.
789 PADOFFSET pad_findmy(const char* name)
794 =item pad_fixup_inner_anons
795 X<pad_fixup_inner_anons>
797 For any anon CVs in the pad, change CvOUTSIDE of that CV from
798 old_cv to new_cv if necessary. Needed when a newly-compiled CV has to be
799 moved to a pre-existing CV struct.
801 void pad_fixup_inner_anons(PADLIST *padlist, CV *old_cv, CV *new_cv)
809 Free the SV at offset po in the current pad.
811 void pad_free(PADOFFSET po)
819 Cleanup at end of scope during compilation: set the max seq number for
820 lexicals in this scope and warn of any lexicals that never got introduced.
830 Create a new compiling padlist, saving and updating the various global
831 vars at the same time as creating the pad itself. The following flags
832 can be OR'ed together:
834 padnew_CLONE this pad is for a cloned CV
835 padnew_SAVE save old globals
836 padnew_SAVESUB also save extra stuff for start of sub
838 PADLIST* pad_new(int flags)
846 Push a new pad frame onto the padlist, unless there's already a pad at
847 this depth, in which case don't bother creating a new one. Then give
848 the new pad an @_ in slot zero.
850 void pad_push(PADLIST *padlist, int depth)
858 Mark all the current temporaries for reuse
868 Set the entry at offset po in the current pad to sv.
869 Use the macro PAD_SETSV() rather than calling this function directly.
871 void pad_setsv(PADOFFSET po, SV* sv)
879 Abandon the tmp in the current pad at offset po and replace with a
882 void pad_swipe(PADOFFSET po, bool refadjust)
890 Tidy up a pad after we've finished compiling it:
891 * remove most stuff from the pads of anonsub prototypes;
895 void pad_tidy(padtidy_type type)
903 Free the padlist associated with a CV.
904 If parts of it happen to be current, we null the relevant
905 PL_*pad* global vars so that we don't have any dangling references left.
906 We also repoint the CvOUTSIDE of any about-to-be-orphaned
907 inner subs to the outer of this cv.
909 (This function should really be called pad_free, but the name was already
912 void pad_undef(CV* cv)
920 =head1 Stack Manipulation Macros
927 Declare Just C<SP>. This is actually identical to C<dSP>, and declares
928 a local copy of perl's stack pointer, available via the C<SP> macro.
929 See C<SP>. (Available for backward source code compatibility with the
930 old (Perl 5.005) thread model.)
940 True if this op will be the return value of an lvalue subroutine
948 =head1 SV Manipulation Functions
955 Given a chunk of memory, link it to the head of the list of arenas,
956 and split it into a list of free SVs.
958 void sv_add_arena(char* ptr, U32 size, U32 flags)
966 Decrement the refcnt of each remaining SV, possibly triggering a
967 cleanup. This function may have to be called multiple times to free
968 SVs which are in complex self-referential hierarchies.
978 Attempt to destroy all objects not yet freed
988 Deallocate the memory used by all arenas. Note that all the individual SV
989 heads and bodies within the arenas must already have been freed.
991 void sv_free_arenas()
999 =head1 Unicode Support
1003 =item find_uninit_var
1006 Find the name of the undefined variable (if any) that caused the operator o
1007 to issue a "Use of uninitialized value" warning.
1008 If match is true, only return a name if it's value matches uninit_sv.
1009 So roughly speaking, if a unary operator (such as OP_COS) generates a
1010 warning, then following the direct child of the op may yield an
1011 OP_PADSV or OP_GV that gives the name of the undefined variable. On the
1012 other hand, with OP_ADD there are two branches to follow, so we only print
1013 the variable name if we get an exact match.
1015 The name is returned as a mortal SV.
1017 Assumes that PL_op is the op that originally triggered the error, and that
1018 PL_comppad/PL_curpad points to the currently executing pad.
1020 SV* find_uninit_var(OP* obase, SV* uninit_sv, bool top)
1028 Print appropriate "Use of uninitialized variable" warning
1030 void report_uninit(SV* uninit_sv)
1040 The autodocumentation system was originally added to the Perl core by
1041 Benjamin Stuhl. Documentation is by whoever was kind enough to
1042 document their functions.
1046 perlguts(1), perlapi(1)
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